Large Artery Occlusion Treated in Extended Time with Mechanical Thrombectomy Trial

Subjects in intervention group will receive MT as soon as possible. Investigators and clinicians should strive to reduce delays of pre-surgery procedure and follow the local standard guideline of MT during the operation and perioperative period. All CFDA approved devices are allowed in this trial. Angioplasty and stent placement can be performed at the discretion of the physicians. Base on site experience, the randomization-operation start period should be within 60 minutes.